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    SubjectRe: [PATCH] perf: Store active software events in a hashlist
    On Mon, 2010-04-05 at 16:08 +0200, Frederic Weisbecker wrote:
    > Each time a software event triggers, we need to walk through
    > the entire list of events from the current cpu and task contexts
    > to retrieve a running perf event that matches.
    > We also need to check a matching perf event is actually counting.
    > This walk is wasteful and makes the event fast path scaling
    > down with a growing number of events running on the same
    > contexts.
    > To solve this, we store the running perf events in a hashlist to
    > get an immediate access to them against their type:event_id when
    > they trigger.

    So we have a hash-table per-cpu, each event takes a ref on the hash
    table, when the thing is empty we free it.

    When the event->cpu == -1 (all cpus) we take a ref on all possible cpu's
    hash-table (should be online I figure, but that requires adding a
    hotplug handler).

    Then on event enable/disable we actually add the event to the hash-table
    belonging to the cpu the event/task gets scheduled on, since each event
    can only ever be active on one cpu.


    So looks good, altough I think we want to do that online/hotplug thing.

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      Last update: 2010-04-06 17:31    [W:0.045 / U:19.980 seconds]
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